Hoping this helps anyone else:
Bear containers are required on the Mt. Whitney Trail from Memorial Weekend to November 1. I called the Wilderness Permit Office today (760) 873-2483 and they say it's okay to use my AllMitey Ursack
I called since the website requirement was vague: “Containers designed to prevent access by bears are required” per Inyo NF Bear Cannister requirements
Depending on what year you go, you might want to get an update on this requirement from the Wilderness Permit Office.
The Whitney Portal Store at the Whitney Portal Campground rents bear canisters.
Store Hours: May 9am-6pm, June 8am-8pm, July 7am-9pm, August 7am-9pm, September 8am-8pm, October 9am-6pm. Closed November - April.
Just remember to leave enough room in your pack for the canister.
Make sure to remove all food and scented items from your vehicle before you leave. Bears have no problem breaking and entering your car or truck. Keep ice chests and other colorful containers that look like an ice chest out of view. These bears are smart and know what one looks like. There are bear proof storage lockers located at the Whitney Trailhead Parking Lot. Put your name, phone number, and the date on your items before leaving anything in there.